Method for disinfecting air in air ducts

ABSTRACT

The invention relates to a method and a device for disinfecting the air of an air flow ( 2 ) inside an air supply duct ( 1 ) with a nontoxic disinfectant. The disinfectant is sprayed and injected in the injection direction ( 31 ) by means of at least one injection nozzle ( 30 ) of an injection device ( 3 ), the injection direction ( 31 ) approximately corresponding to the direction of the air flow ( 2 ). The injection in the region located after a contraction ( 12 ) in the duct and the related flow acceleration enables an absorption of the particles on the inner walls ( 100 ) of the air supply duct ( 1 ), over the entire length of the air supply duct ( 1 ).

TECHNICAL FIELD

The present invention describes a method for disinfecting the air of an air flow in an air supply duct, in particular of an air-conditioning system with a non-toxic disinfectant.

PRIOR ART

The closest prior art is EP0615603, which discloses a method and a device for disinfecting air in air supply ducts of an air-conditioning system. A non-toxic disinfectant is injected into an air supply duct counter to an air flow by means of an injection device.

The non-toxic disinfectant used kills fungi, algae, bacteria and similar organisms and is not only effective in the air flow itself but, as it is deposited on the inner walls of the air supply duct, acts in the long term on the germs deposited on the inner walls, so they no longer pass into the air flow.

The disclosed method describes the disinfection of the air in the region of the injection device. The particles of the disinfectant are injected into the air supply duct in the direction of the air flow and the particles are ionised by means of ionisation means. The injection counter to the air flow means that cloud formation around the injection nozzles results, some of the particles being thrown against the adjacent inner walls of the air supply duct in the vicinity of the injection device and being deposited there, preferably in a heaped manner.

Injected particles are electrically charged owing to the additional ionisation of the particles by ionisation means and, because the air supply duct is earthed, conducted rapidly in the direction of the inner wall of the air supply duct. The ionised particles are thereby deposited onto the inner walls of the air supply duct in the region of the injection nozzle shortly after exiting and therefore do not move around in the air supply duct. A disinfection, which is locally limited to the site of the injection, of the air thus takes place in the region of the injection device. Associated with this are disruptive deposits of the particles in the vicinity of the injection device. The locally disinfected air is circulated in the air supply duct after the disinfection which has taken place in the vicinity of the injection device and is not disinfected further, as the range of the particles inside the air supply duct is limited.

The results achieved were only satisfactory initially and in new systems. After a certain time, disruptive deposits, which can also become centres for germs, form in the air supply ducts at different distances from the injection devices.

PRESENTATION OF THE INVENTION

The object of the present invention is to create a method and a device for disinfecting air in air supply ducts, which allow particles of a disinfectant to be distributed as homogeneously as possible on the inner walls of the air supply duct over virtually the entire length of the air supply ducts.

This object and additionally the avoidance of disruptive locally accumulated deposits on the inner wall in the region of the injection nozzles is achieved by the device according to the invention and the method according to the invention. The injection effects a connection of the disinfectant in the air and then its deposition on the duct inner walls.

In a preferred configuration, the disinfectant has a retentive behaviour, which allows its distribution in the entire duct and thus sterilisation of all the inner walls. In the results of conducted tests, the air moves multiple times (approx. 5-6 times) faster in the duct than the particles of the disinfectant, which, owing to their inertia, are deposited on the duct inner walls, entrained again by the air flow and deposited again at another point. This process can be repeated, which allows sufficiently complete wetting and sterilisation of the duct inner walls.

As a result of the ionisation and static charge of the air molecules, all micro-organisms are affected. However, ozone formation must be avoided, as ozone destroys the disinfectant or its components.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of the subject matter of the invention is described below in connection with the attached drawings.

FIG. 1 shows a schematic view of an air supply duct.

FIG. 2 shows a schematic view of a section of a curved air supply duct, whereas

FIG. 3 shows a schematic view of a straight air supply duct with a chicane for manipulating the air flow.

DESCRIPTION

FIG. 1 shows part of an air supply duct 1, the air flow 2 being indicated with arrows 2. In the air supply duct 1, a flow sensor 4 and an injection device 3 having at least one injection nozzle 30 for atomising and injecting the disinfectant are installed one behind the other in the flow direction 2. Further down the air supply duct 1, further injection devices 3 can be provided, which are not shown here. The method and the device described here can be used in particular in air-conditioning systems.

These elements are connected by electrical lines 7 to a regulation device 8. The injection device 3 having the at least one injection nozzle 30 is connected to a pipeline 9 which leads to a pump 10, which pumps disinfectant dissolved in water from a reservoir 11 to the at least one injection nozzle 30. The flow sensor 4 can switch off the pump 10 when the air flow 2 falls below a certain threshold value. Moreover, the pump operation can be adapted to the air flow rate.

The mist of disinfectant produced by the at least one injection nozzle 30 consists of particles having a size of approximately 50 μm, which are injected in an injection direction 31 in the direction of the air flow 2. Owing to this injection in the direction of the air flow 2 inside the air supply duct 1, particles can be transported far through the air supply duct 1, in the best case through the entire air supply duct 1, before they are deposited on the inner walls 100, where they have their disinfectant effect for longer periods.

It is advantageous to carry out the injection in a region downstream of a flow acceleration at a site at which a lower flow speed but a higher pressure prevails.

In FIG. 1, the injection device 3 is arranged in such a manner that part of the air flow 2 is covered, as a result of which a higher flow speed results at a narrowed portion 12. As known in a Venturi tube, a pressure difference prevails between the narrowed portion 12 of the air supply duct 1 and the regions with maximum cross-sectional area 13.

In the region of the narrowed portion 12, the disinfectant is injected in an atomised manner through the injection nozzle 30, as a result of which particles are carried over great distances with the air flow 2 owing to the high flow speed. The high flow speed prevents immediate adsorption of the particles on the inner walls 100 of the air supply duct 1.

The curvature of the air supply duct 1 shown in Figure results in an acceleration of the flow, a higher pressure p1 prevailing on the side of the smaller radius of curvature, at the exit region of the curve. The pressure p2 at the narrowed portion 12 on the side of the larger radius is less than the pressure p1, and a correspondingly high flow speed of the air flow 2 is present at this point. The high flow speed entrains atomised particles of the disinfectant, as a result of which a desirable distribution of the disinfectant can also be achieved in regions a long way away from the injection device 3. This arrangement of the injection device 3 in the region of a narrowed portion 12 ensures that particles are distributed virtually homogeneously in the air supply duct 1 before they are adsorbed on the inner walls 100.

In a further embodiment, which allows disinfectant to be deposited over the entire length of the air supply duct 1, a chicane 5 is used, which is arranged inside the cross section of the air supply duct 1. This is shown schematically in FIG. 3. The chicane 5 forms a narrowed portion 12 in the air supply duct 1 and forces the air flow 2 in a targeted manner in the direction through the narrowed portion 12, a pressure difference between p1 and p2 resulting in this case too. The injection takes place downstream of the chicane 5 through at least one injection nozzle 30, as a result of which atomised disinfectant is deposited in wide regions of the air supply duct 1. The chicane 5 can also be omitted in this embodiment.

If the air is to be humidified, water can be evaporated at a suitable point in the air supply duct 1, the amount of which is regulated by the regulation device 8 with the aid of a humidity sensor. The same disinfectant is preferably added to the water in order to prevent introduction of fungi or algae etc.

As the air flow ultimately reaches the working or living space from the air supply duct 1, the disinfectant should comply with the strictest health control requirements. It should never contain any mercury, phenol or similar substances, or alcohol.

A biocide product comprising lactic acid, vitamin C and citric acid, available under the commercial name “OLLOSTAT” of the applicant, is for example used as a preferred disinfectant for use in the method according to the invention and the device. This disinfectant has been approved for use as a disinfectant by the Swiss Federal Office of Public Health.

LIST OF REFERENCE SYMBOLS

-   1 Air supply duct -   100 Inner wall -   2 Air flow (arrow) -   3 Injection device -   30 Injection nozzle -   31 Injection direction (arrow) -   4 Flow sensor -   5 Chicane -   7 Electrical lines -   8 Regulation device -   9 Pipeline -   10 Pump -   11 Reservoir -   12 Narrowed portion -   13 Maximum cross-sectional area 

1. A method for disinfecting the air of an air flow (2) in an air supply duct (1), in particular of an air-conditioning system with a non-toxic disinfectant, wherein atomisation of the disinfectant into particles and injection of the particles by means of at least one injection nozzle (30) of an injection device (3) in an injection direction (31), wherein the injection direction (31) corresponds approximately to the direction of the air flow (2), and distribution of the particles of the disinfectant in the air flow (2), and subsequent adsorption of the particles to the inner walls (100) can be achieved over the entire length of the air supply duct (1).
 2. A method for disinfecting the air of an air flow (2) in an air supply duct (1), in particular of an air-conditioning system with a disinfectant, wherein the air is ionised in the duct, at least the disinfectant particles in the air are electrically charged, while the duct walls are kept at earth potential, so that the charged particles are deposited more rapidly onto the duct walls, wherein atomisation of the disinfectant into particles and injection of the particles by means of at least one injection nozzle (30) of an injection device (3) in an injection direction (31), wherein the injection direction (31) corresponds approximately to the direction of the air flow (2), and distribution of the particles of the disinfectant in the air flow (2) and subsequent deposition of the particles on the inner walls (100) is achieved over the entire length of the air supply duct (1).
 3. The method for disinfecting air according to claim 1, wherein the injected disinfectant behaves in a retentive manner.
 4. The method for disinfecting air according to claim 1, wherein the injection takes place in a region downstream of a narrowed portion (12) and thus an acceleration in flow, wherein the pressure (p1) downstream of the flow acceleration is greater than the pressure (p2) in the region of the narrowed portion (12).
 5. The method for disinfecting air according to claim 3, wherein the acceleration in flow is achieved by the arrangement of the injection device (3) inside the air supply duct (1).
 6. The method for disinfecting air according to claim 3, wherein the acceleration in flow is achieved by a curvature of the air supply duct (1), wherein the injection device (3) is arranged on the side of the smaller radius in the exit region of the curve.
 7. The method for disinfecting air according to claim 3, wherein the acceleration in flow is achieved by a chicane (5) which is arranged inside the air supply duct (1).
 8. The method according to claim 1, wherein a biocide product, in particular comprising a proportion of lactic acid, vitamin C and a proportion of citric acid is used as the disinfectant.
 9. A device for disinfecting air according to the method according to claim 1, wherein at least one injection nozzle (30) is provided on the injection device (3), which can be supplied with a disinfectant via a pipeline (9) and a pump (10) from a reservoir (11).
 10. The device according to claim 9, wherein the atomised and injected amount of the disinfectant can be varied in a controlled manner by a regulation device (8) by means of electrical lines (7). 